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Amorphous materials have no long-range order, but there are ordered structures at short range (2–5 Å), medium range (5–20 Å) and even longer length scales 1 – 5 . While regular 6 , 7 and semiregular polyhedra 8 – 10 are often found as short-range ordering in amorphous materials, the nature of medium-range order has remained elusive 11 – 14 . Consequently, it is difficult to determine whether there exists any structural link at medium range or longer length scales between the amorphous material and its crystalline counterparts. Moreover, an amorphous material often crystallizes into a phase of different composition 15 , with very different underlying structural building blocks, further compounding the issue. Here, we capture an intermediate crystalline cubic phase in a Pd-Ni-P amorphous alloy and reveal the structure of the medium-range order, a six-membered tricapped trigonal prism cluster (6M-TTP) with a length scale of 12.5 Å. We find that the 6M-TTP can pack periodically to several tens of nanometres to form the cube phase. Our experimental observations provide evidence of a structural link between the amorphous and crystalline phases in a Pd-Ni-P alloy at the medium-range length scale and suggest that it is the connectivity of the 6M-TTP clusters that distinguishes the crystalline and amorphous phases. These findings will shed light on the structure of amorphous materials at extended length scales beyond that of short-range order. An intermediate cube phase with a medium-range order structure is identified in Pd-Ni-P metallic glass, which links the amorphous and crystalline phases.

Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. Amorphous silicon monoxide is known to undergo disproportionation to silicon- and silicon dioxide-like regions, however direct observation of the atomic-scale heterogeneity is still missing. Here, the authors use angstrom-beam electron diffraction to reveal precise structural details of this unusual material.

Amorphous alloys, also known as metallic glasses, are solid metallic materials having long-range disordered atomic structures. Compared to crystalline alloys, amorphous alloys not only have metallic characters, but also possess several distinct properties associated to the amorphous structure, such as isotropy, composition flexibility, unsaturated surface, etc. As a result, amorphous alloys offer a class of highly promising materials for catalyzing electrochemical reactions. In this minireview, the preparation, characterization and electrocatalytic performances of a variety of metallic amorphous alloy materials are summarized. The influences of the amorphous alloy structure on different electrochemical reactions are discussed. Finally, a summary on the advantages and challenges of amorphous alloys in electrocatalysis is provided, along with some perspectives about the future research directions.

Amorphous interfacial complexions are particularly resistant to radiation damage and have been primarily studied in alloys with good glass-forming ability, yet recent reports suggest that these features can form even in immiscible alloys such as Cu-Ta under irradiation. In this study, the mechanisms of damage production and annihilation due to primary knock-on atom collisions are investigated for amorphous interphase and grain boundaries in a Cu-Ta alloy using atomistic simulations. Amorphous complexions, in particular amorphous interphase complexions that separate Cu and Ta grains, result in less residual defect damage than their ordered counterparts. Stemming from the nanophase chemical separation in this alloy, the amorphous complexions exhibit a highly heterogeneous distribution of atomic excess volume, as compared to a good glass former like Cu-Zr. Complexion thickness, a tunable structural descriptor, plays a vital role in damage resistance. Thicker interfacial films are more damage-tolerant because they alter the defect production rate due to differences in intrinsic displacement threshold energies during the collision cascade. Overall, the findings of this work highlight the importance of interfacial engineering in enhancing the properties of materials operating in radiation-prone environments and the promise of amorphous complexions as particularly radiation damage-tolerant microstructural features.

The new type of Fe 83 − x Si 2.5 B 12 P 2.5 C x (x = 0, 0.5, 1.0, 1.5, 2.0 at%) amorphous soft magnetic system with low cost, high saturation magnetization and low coercivity were designed and prepared by means of rapid quenching. The effect of C on the amorphous formability, thermal stability, and soft magnetic properties in the alloy system were studied. Results suggest that the addition of small atom C can promote the formation of densely atomic structure of alloy, thereby promoted the enhancement of amorphous formability. With the increase of C content, the temperature interval between two crystallization peaks increases first and then decreases. When C content is 1.0 at%, Δ T ( T x2 - T x1 ) reaches the maximum value, of about 109.9 ℃, which is beneficial to enhance the thermal stability and soft magnetic properties. As the concentration of C is raised, the B s exhibit a pattern of increases followed by a subsequent decrease, while coercivity changes in the opposite way. When the C content is 1.0 at%, the B s of the alloy reaches the highest value of 1.78 T and the coercivity exhibits the best which is 14.055 A/m. The results offer important contributions to the design and advancement of high B s amorphous soft magnetic materials for industrial applications involving amorphous electric motors.

We combine an analytically solvable mean-field elasto-plastic model with molecular dynamics simulations of a generic glass former to demonstrate that, depending on their preparation protocol, amorphous materials can yield in two qualitatively distinct ways. We show that well-annealed systems yield in a discontinuous brittle way, as metallic and molecular glasses do. Yielding corresponds in this case to a first-order nonequilibrium phase transition. As the degree of annealing decreases, the first-order character becomes weaker and the transition terminates in a second-order critical point in the universality class of an Ising model in a random field. For even more poorly annealed systems, yielding becomes a smooth crossover, representative of the ductile rheological behavior generically observed in foams, emulsions, and colloidal glasses. Our results show that the variety of yielding behaviors found in amorphous materials does not necessarily result from the diversity of particle interactions or microscopic dynamics but is instead unified by carefully considering the role of the initial stability of the system.

Amorphous materials inherit short- and medium-range order from the corresponding crystal and thus preserve some of its properties while still exhibiting novel properties 1 , 2 . Due to its important applications in technology, amorphous carbon with sp 2 or mixed sp 2 – sp 3 hybridization has been explored and prepared 3 , 4 , but synthesis of bulk amorphous carbon with sp 3 concentration close to 100% remains a challenge. Such materials inherit the short-/medium-range order of diamond and should also inherit its superior properties 5 . Here, we successfully synthesized millimetre-sized samples—with volumes 10 3 –10 4 times as large as produced in earlier studies—of transparent, nearly pure sp 3 amorphous carbon by heating fullerenes at pressures close to the cage collapse boundary. The material synthesized consists of many randomly oriented clusters with diamond-like short-/medium-range order and possesses the highest hardness (101.9 ± 2.3 GPa), elastic modulus (1,182 ± 40 GPa) and thermal conductivity (26.0 ± 1.3 W m −1  K −1 ) observed in any known amorphous material. It also exhibits optical bandgaps tunable from 1.85 eV to 2.79 eV. These discoveries contribute to our knowledge about advanced amorphous materials and the synthesis of bulk amorphous materials by high-pressure and high-temperature techniques and may enable new applications for amorphous solids. Preparing amorphous phases of carbon with mostly sp 3 bonding in bulk is challenging, but macroscopic samples that are nearly pure sp 3 are synthesized here by heating fullerenes at high pressure.

Many problems associated with Li–S and Na–S batteries essentially root in the generation of their soluble polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS₃ as such a material for room-temperature Li–S and Na–S batteries. In Li–S batteries, MoS₃ exhibits sulfur-like behavior with large reversible specific capacity, excellent cycle life, and the possibility to achieve high areal capacity. Most remarkably, it is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C. MoS₃ can also be used as the cathode material of even more challenging Na–S batteries to enable decent capacity and good cycle life. Operando X-ray absorption spectroscopy (XAS) experiments are carried out to track the structural evolution of MoS₃. It largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates.

Amorphous solids such as glass, plastics and amorphous thin films are ubiquitous in our daily life and have broad applications ranging from telecommunications to electronics and solar cells 1 – 4 . However, owing to the lack of long-range order, the three-dimensional (3D) atomic structure of amorphous solids has so far eluded direct experimental determination 5 – 15 . Here we develop an atomic electron tomography reconstruction method to experimentally determine the 3D atomic positions of an amorphous solid. Using a multi-component glass-forming alloy as proof of principle, we quantitatively characterize the short- and medium-range order of the 3D atomic arrangement. We observe that, although the 3D atomic packing of the short-range order is geometrically disordered, some short-range-order structures connect with each other to form crystal-like superclusters and give rise to medium-range order. We identify four types of crystal-like medium-range order—face-centred cubic, hexagonal close-packed, body-centred cubic and simple cubic—coexisting in the amorphous sample, showing translational but not orientational order. These observations provide direct experimental evidence to support the general framework of the efficient cluster packing model for metallic glasses 10 , 12 – 14 , 16 . We expect that this work will pave the way for the determination of the 3D structure of a wide range of amorphous solids, which could transform our fundamental understanding of non-crystalline materials and related phenomena. A method that achieves atomic-resolution tomographic imaging of an amorphous solid enables detailed quantitative characterization of the short- and medium-range order of the three-dimensional atomic arrangement.

Accurately identifying the local structural heterogeneity of complex, disordered amorphous materials such as amorphous silicon is crucial for accelerating technology development. However, short-range atomic ordering quantification and nanoscale spatial resolution over a large area on a-Si have remained major challenges and practically unexplored. We resolve phonon vibrational modes of a-Si at a lateral resolution of <60 nm by tip-enhanced Raman spectroscopy. To project the high dimensional TERS imaging to a two-dimensional manifold space and categorize amorphous silicon structure, we developed a multiresolution manifold learning algorithm. It allows for quantifying average Si-Si distortion angle and the strain free energy at nanoscale without a human-specified physical threshold. The multiresolution feature of the multiresolution manifold learning allows for distilling local defects of ultra-low abundance (< 0.3%), presenting a new Raman mode at finer resolution grids. This work promises a general paradigm of resolving nanoscale structural heterogeneity and updating domain knowledge for highly disordered materials. Short range atomic ordering quantification and nanoscale spatial resolution over a large area for amorphous materials is crucial for accelerating technology development but remain challenges. Here, the authors explore nanoscale heterogeneity of amorphous silicon by tip-enhanced Raman spectroscopy via multiresolution manifold learning.